On Sunday, April 15, 2012 09:24:08 PM Kirk Wallace did opine: > I have some scope traces from LinuxCNC's pump below. I haven't had time > to add text to the pictures yet but I'll try to describe them in this > message for now. The group of pictures is here: > http://wallacecompany.com/machine_shop/G540/ > > ------------ > Motherboard port, set to SPP in BIOS: > http://wallacecompany.com/machine_shop/G540/g540_mb_spp.jpg > > one trace is at 0 V, vertical divisions are 1 V per div., green LED OFF > > ------------ > Motherboard port, set to EPP in BIOS: > http://wallacecompany.com/machine_shop/G540/g540_mb_epp.jpg > > green LED ON > > ------------ > Rosewill PCI card, set to SPP and EPP, I get the same trace either way: > http://wallacecompany.com/machine_shop/G540/g540_rw_sepp.jpg > > green LED OFF > > ------------ > Rosewill PCI card, with 1k Ohm pull-up: > http://wallacecompany.com/machine_shop/G540/g540_rw_1kpup.jpg > > green LED ON > > ------------ > Startech PCI card, set to SPP: > http://wallacecompany.com/machine_shop/G540/g540_st_spp.jpg > > green LED OFF > > ------------ > Startech PCI card, set to EPP: > http://wallacecompany.com/machine_shop/G540/g540_st_epp.jpg > > swings all the way to 5 V, green LED ON > > ------------ > SIIG PCI card, set to SPP and EPP, I get the same trace either way: > http://wallacecompany.com/machine_shop/G540/g540_siig_spp.jpg > > just enough to turn green LED ON > > ------------ > SIIG PCI card, with 330 Ohm pull-up, set to SPP and EPP, I get the same > trace either way: > http://wallacecompany.com/machine_shop/G540/g540_siig_k33pup.jpg > > green LED ON > > ------------ > > Horizontal divisions are 50 microseconds/div. One cycle is 4 div. or > 20kHZ (?) (base-thread = 100000ns, with reset = 1000).
What happens if the pump frequency is reduced to say 10% of what its set at now? Looking at the scope traces, either the probe is way out of calibration against the scopes own test square wave, or the 540 has a low value series resistor, 33-120 ohm range, with several hundred pf on the other side of the resistor as a noise filter on that input, and likely on all inputs since engineers have a tendency to 'step & repeat' for that stuff. I can't believe you would long tolerate a probe that far out of adjustment Kirk, so that leaves the 540 apparently suffering from way too much noise filtering on that input. So the pumping frequency is so high the capacitor used for noise filtering never has a chance to either fully charge, or to fully discharge. So you get insufficient swing. So drop the pump frequency to 10-20% of what it is now just for effects, would be my advice. If it drops out because the pump is then too slow, the 540 needs a redesign tweak, at least according to Gene. :) Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> Write yourself a threatening letter and pen a defiant reply. ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
